The invention relates to the field of compositions useful for the prevention and treatment of coccidiosis in animals, methods of using such compositions and animal comestibles containing such compositions.
Coccidiosis is a disease caused by microscopic protozoal parasites called coccidia, belonging to the genus Eimeria. The infection in the host animals is initiated by the ingestion, usually along with food, water, and/or fecal material, of Eimeria organisms in the sporulated oocyst stage. When the ingested oocysts enter the intestine, the infectious stage of the Eimeria soon develops from the oocysts and causes extensive damage to the inner walls of the intestine and the cecum or "intestinal pouch." Cecal coccidiosis in chickens, for example, is caused primarily by the organism E. tenella and results in the destruction of the cecal linings of the host.
Intestinal coccidiosis in chickens results primarily from other species of Eimeria, E. necatrix, E. acervulina, E. maxima, E. brunetti, E. hagani, E. praecox, E. mitis, etc. E. gallopavonis, E. meleagrimitis, E. adenoeides, E. meleagridis, E. dispersa, E. innocua, E. subrotunda, etc., cause coccidiosis infections in turkeys. In the duck and goose, E. truncata, E. anseris, etc., in cattle, E. bovis, E. zurenii, E. alabamensis, E. auburnensis, etc., in sheep, E. ahsata, E. parva, E. faurei, E. arloingi, etc., in pigs, E. debliecki, E. spinosa, etc. cause coccidiosis.
Coccidiosis affects animals such as domestic animals and animals raised commercially for food. Even if such animals survive the infection, serious economic losses still result due to a reduced efficiency in feed utilization and consequent slower growth than normal. Coccidiosis is an especially serious problem in the case of animals raised for food purposes and if not controlled causes serious economic loss in the raising of these animals.
A number of coccidiostatic agents are presently available for the prevention and/or treatment of coccidiosis. Still, many of these agents have certain shortcomings. Animals treated with some of the known coccidiostats sometimes show reduced feed efficiency and lower weight gains than normal. Moreover, the development of resistance to the more commonly used agents is becoming an increasingly significant problem; one which is becoming a limiting factor in successfully combatting coccidiosis. Still other, particularly newer and more potent ionophoric agents, have very narrow safety and efficacy ranges with resulting toxicity risks for treated animals, as well as for other farm animals and man by virtue of incidental or accidental exposure or ingestion.
The most widely used commercially available coccidiostats belong to the group of polyether antibiotics isolated from various strains of bacteria. They are characterized by the cyclic ether moieties in their chemical structures. Examples include monensin, lasalocid, salinomycin, lonomycin and narasin. These antibiotics are also known to those skilled in the art as "ionophores" for what is believed to be their transport-inducing mode of action.
Recently a non-ionophorous antibiotic produced from Streptomyces roseofulvus, frenolicin B, has been shown to have some anticoccidial activity against E. tenella in chickens (Omura, et al., J. Antibiotics, Vol. 38, No. 10, pp. 1447-8 (1985)). Frenolicin B is a naphthoquinone antibiotic having the following structure: ##STR1##